Nowadays, Google is giving much preference to 2 particular factors. 1. Quality, Unique and Interesting Page content 2. Inbound links from quality, relevant and authority sites (one way are much preferable than others)
Is it time to give each of these keyword phrases a separate page and optimize?
I would suggest you to do that. From my experience I can say that now a days visitors are using very specific search terms and for that reason Google is also giving rank to those pages which are very specific with the Search Term. Don't know may be I am wrong,but this is what I feel.
I notice other websites in same industry also have more than one keyword phrase in home page title, but rank on top. Some even have less inbound links than I do.
May be content of other sites are excellent or quality of inbound links are high.